Incredible photos taken with drones and satellites reveal dozens of circular designs etched into the ground near an abandoned city.

The designs, known as geoglyphs, can be as small as six feet across, or as large as 800 square metres – about the size of two NBA basketball courts.

And while experts believe they know how the strange swirls were made, they can only speculate about what purpose they could have served.

JUSTIN JENNINGS

SYMBOLIC: It's been suggested that they had something to do with trade

“They were created by removing surface stones to expose the sandy soil”

Justin Jennings

Justin Jennings, a curator at the Royal Ontario Museum in Toronto, Canada, led the team that discovered the geoglyphs in Peru.

The shapes, which were found near the lost city of Quilcapampa, date back to some time between 1050 and 1400 AD.

At that time, the city sprawled over 173-acres and was a hub for trade, Dr Jennings told the Seeker website.

Some of the paths used for that trade lie close to the mysterious designs, which had led to one theory.

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It's been suggested that the flow of goods through the town is represented by the swirling shapes.

Yet nobody can say for sure what they mean, as no writing system existed in Peru at the time.